Patent Literature 1 discloses a tilt-trim device of an outboard motor that generates power by extension/contraction operation of a hydraulic cylinder device. The tilt-trim device includes: a clamp bracket fixed to a transom of a hull; a swivel bracket pivotally supported onto the clamp bracket so as to be swingable in a vertical direction; and a hydraulic cylinder device disposed between the clamp bracket and the swivel bracket. The outboard motor including a propeller and an engine is pivotally supported onto the swivel bracket so as to be swingable in a horizontal direction. The hydraulic cylinder device is caused to perform extension/contraction operation, and thus the swivel bracket tilts in the vertical direction with respect to the clamp bracket, thereby being capable of raising/lowering the outboard motor out of/into water.
Further, the tilt-trim device not only raises/lowers the outboard motor out of/into water, but also functions to protect the outboard motor from a sudden external force. That is, there is assumed a case where the outboard motor collides with obstacles such as driftwood, or hits underwater obstacles such as sunken rocks while the hull sails on water, and hence in a case where collision energy is applied to the outboard motor, it is necessary to immediately release restraining of the swivel bracket by the hydraulic cylinder device. Accordingly, a plurality of ball valves that open and close in accordance with a change in oil pressure in a cylinder are provided to the hydraulic cylinder device, and thus irrespective of operation of an oil pump, the hydraulic cylinder device can freely extend and contract in response to a sudden external force.